Sheet container, image forming apparatus and sheet stacking method

ABSTRACT

A sheet container includes a case configured to contain a plurality of sheets stacked in a stacking direction, a first regulating member configured to regulate a first side of the sheets along a first direction perpendicular to the stacking direction, a second regulating member configured to regulate a second side perpendicular to the first side along a second direction perpendicular to the stacking direction and the first direction, the second regulating member to form a rectangular area with the first regulating member under the sheets, a tray configured to support a lower surface of a lowermost sheet of the sheets, and a guide member inclined with respect to the stacking direction, the first direction and the second direction on the rectangular area, and formed higher from a position lower than the lower surface of the lowermost sheet as approaching a closest corner in the rectangular area.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from US provisional application 61/187175, filed on Jun. 15, 2009, the entire contents of which are incorporated herein by reference.

FIELD

This specification relates to a sheet container for containing sheets to be supplied to an image forming section in an image forming apparatus.

BACKGROUND

An image forming apparatus includes a sheet feeding cassette (container) for stacking sheets or the like as a part of a sheet feeding device. The sheet feeding cassette includes a plate-like sheet tray for placing thereon the sheets in a sheet stacking area. One end side of the sheet tray is rotatably supported to the sheet feeding cassette, and the sheet tray is rotated around a rotation shaft by a drive mechanism such as a motor so that the other end side is raised. When the sheet tray is raised, the sheet stacked on the sheet tray contacts a pickup roller, and when the pickup roller is driven in this state, the sheet can be successively conveyed from the sheet feeding cassette to an image forming section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural view showing a structure of an MFP (Multi Function Peripheral) as an image forming apparatus.

FIG. 2 is a perspective view of a sheet cassette of this embodiment.

FIG. 3 is an enlarged perspective view of a portion of the sheet cassette surrounded by a broken line A in FIG. 2.

FIG. 4 is a sectional view of the sheet cassette at an arrow B-B position in FIG. 2.

FIG. 5 is a sectional view of the sheet cassette at an arrow C-C position in FIG. 3.

FIG. 6 is a sectional view of the sheet cassette at an arrow D-D position in FIG. 3.

FIG. 7 is a perspective view of the sheet cassette seen from a downstream side in a sheet supply direction.

DETAILED DESCRIPTION

According to an embodiment, a sheet container includes a case to contain a plurality of sheets stacked in a stacking direction, a first regulating member to regulate a first side of the sheets along a first direction perpendicular to the stacking direction, a second regulating member to regulate a second side perpendicular to the first side along a second direction perpendicular to the stacking direction and the first direction, a tray to support a lower surface of a lowermost sheet of the sheets, and a guide member having, in a rectangular area which is defined by the first regulating member and the second regulating member and in which the sheets are stacked, an inclined surface which is inclined with respect to any of the stacking direction, the first direction and the second direction, and becomes higher from a position lower than the lower surface of the lowermost sheet as approaching a closest corner in the rectangular area.

Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a structural view showing a structure of an MFP (Multi Function Peripheral) 1 as an image forming apparatus. The MFP 1 includes a processor 2, a memory 4, a HDD 6, an image forming section 1A to form an image on a sheet such as a paper or an OHP sheet, a sheet supply section 1B to supply the sheet to the image forming section 1A, an image reading section 1C to read a document, and the like.

The processor 2 is a processing device to control various processes in the image forming section 1A, the sheet supply section 1B, the image reading section 10 and the like. The processor 2 executes programs stored in the memory 4 and the HDD 6 to realize various functions, and executes the processes. As the processor 2, a CPU (Central Processing Unit), an MPU (Micro Processing Unit) capable of executing arithmetic processing equivalent to that of the CPU, or the like is used. A part or the whole of the functions of the MFP 1 may be realized by an ASIC (Application Specific Integrated Circuit) as a processor.

The memory 4 stores programs for the processor 2 to execute processes such as an image forming process in the image forming section 1A, a sheet supply process in the sheet supply section 1B, and an image reading process in the image reading section 1C. As the memory 4, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a DRAM (Dynamic Random Access Memory), a SRAM (Static Random Access Memory), a VRAM (Video RAM), a flash memory or the like is used.

The HDD 6 is an auxiliary storage device to store various information in the MFP 1. The auxiliary storage device of the MFP 1 is not limited to the HDD, and a magnetic disk other than the HDD, such as, for example, a flash memory or a SSD (Solid State Drive), may be used.

The image forming section 1A includes a transfer belt 100 to transfer a developer image to a sheet conveyed by the sheet supply section 1B and a fixing device 102 to perform a fixing process of the developer image on the sheet to the sheet.

The sheet supply section 1B includes plural sheet cassettes 10, as sheet containers, to contain sheets, and pickup rollers 50 to pick up the sheets stacked on the sheet cassettes 10 one by one. The MFP 1 shown in FIG. 1 includes the four sheet cassettes 10.

The image reading section 10 is a general image reading device provided in a copying machine or an image scanner, and reads a document.

Next, a structure of the sheet cassette 10 of the sheet supply section 1B of the embodiment will be described in detail. FIG. 2 is a perspective view of the sheet cassette 10 of the embodiment, FIG. 3 is an enlarged perspective view of a portion of the sheet cassette 10 surrounded by a broken line A in FIG. 2, and FIG. 4 is a sectional view of the sheet cassette 10 at an arrow B-B position in FIG. 2.

The sheet cassette 10 of the embodiment includes a cassette case 12 as a case, a sheet tray 14 as a tray, a first side guide 16 a, a second side guide 16 b, an end guide 18, and a sheet edge guide 20 as a guide member.

The cassette case 12 includes side wall sections 12 a and 12 b opposite to each other in a Y-axis direction, side wall sections 12 c and 12 d opposite to each other in an X-axis direction, a bottom 12 e and the like, and forms a space for containing sheets. The outside of the side wall section 12 a is a front cover 120 as a part of the outer covering of the MFP 1. The front cover 120 includes a pull 120 a for extracting the sheet cassette 10 from the MFP 1. The side wall section 12 c of the embodiment defines a reference position in the X-axis direction for one edge of the sheet contained in the cassette case 12.

One of the first side guide 16 a or the second side guide 16 b and the end guide 18 or the side wall section 12 c functions as a first regulating member to regulate one side of a sheet, and the other functions as a second regulating member to regulate a side perpendicular to the side regulated by the first regulating member.

The sheet tray 14 is a tray for stacking sheets. As shown in FIG. 4, a rotation shaft 14 a supports the sheet tray 14 so that the sheet tray rotates with respect to the side wall section 12 a and the side wall section 12 b opposite to each other in the Y-axis direction. The sheet tray 14 is rotated around the rotation shaft 14 a by a push-up lever 15 rotated by drive force of a motor, and the edge thereof at the side wall section 12 c side is raised. When the push-up lever 15 pushes up the sheet tray 14, the sheet on the sheet tray 14 contacts the pickup roller 50. The pickup roller 50 picks up the sheets one by one in a sheet supply direction (X-axis direction in FIG. 1 and FIG. 2) as a direction along the guide surface of the first side guide 16 a and the second side guide 16 b, and supplies them to the image forming section 1A. The sheet tray 14 has a shape avoiding an area where the first side guide 16 a, the second side guide 16 b and the end guide 18 are moved. Specifically, the sheet tray 14 includes an opening 14 b corresponding to a movement area of the first side guide 16 a, an opening 14 c corresponding to a movement area of the second side guide 16 b, and a recess 14 d corresponding to a movement area of the end guide 18. The first side guide 16 a, the second side guide 16 b and the end guide 18 can be moved through the opening 14 b, the opening 14 c and the recess 14 d in the area overlapping with the area of the contained sheets. Incidentally, a frame-like portion of the sheet tray 14 sandwiched between the side wall section 12 c and the opening area of the opening 14 b is a leading edge support section to support the leading edge of the sheet on the sheet tray 14.

Besides, the sheet tray 14 of this embodiment includes a cushion member 14 e in an area at the rotation shaft 14 a side in a bottom surface facing the bottom 12 e of the cassette case 12. The object of the cushion member is as follows. The sheet cassette 10 can be generally pulled out from the MFP 1 in order to facilitate replenishment of sheets. However, when the sheet cassette 10 is pulled out from the MFP 1 in the state where the sheet tray 14 is pushed up, coupling between the push-up lever 15 to push up the sheet tray 14 and the drive mechanism such as the motor to drive the push-up lever 15 is released, and the sheet tray 14, together with the push-up lever 15, drops. When the sheet tray 14 drops, the sheet tray 14 collides with the bottom 12 e of the cassette case 12, and a collision sound is generated. However, when the foregoing cushion member 14 e is provided, when the sheet tray 14 drops, the cushion member 14 e between the bottom of the sheet tray 14 and the cassette case 12 is nipped and elastically deformed, the rotation speed (dropping speed) of the sheet tray 14 is reduced, and the collision sound can be suppressed. Incidentally, this specification includes the contents disclosed in U.S. patent application Ser. No. 12/543765 with respect to the sheet cassette including the cushion member.

Next, each of the first side guide 16 a and the second side guide 16 b includes two divided wall sections formed on a common base section. The first side guide 16 a and the second side guide 16 b position the edge of the sheet stacked on the sheet tray 14 in the Y-axis direction by a guide surface of the wall section of the first side guide 16 a and a guide surface of the wall section of the second side guide 16 b, which are opposite to each other in the Y-axis direction. Specifically, the first side guide 16 a at the side wall section 12 b side and the second side guide 16 b at the side wall section 12 a side slide in linkage with each other while keeping a distance from an intermediate position between one guide surface and the other guide surface opposite to each other. The sheet is placed on the sheet tray 14, the first side guide 16 a and the second side guide 16 b slide, and the guide surfaces of both are made coincident with both edge positions of the sheet, so that the position of the sheet can be made coincident with the center position of the sheet tray 14 in the Y-axis direction. Incidentally, the Y-axis direction of the sheet stacked on the sheet tray 14 is a width direction of the sheet which is a direction perpendicular to the sheet supply direction.

The structure of the first side guide 16 a will be further described with reference to FIG. 2 and FIG. 3. The first side guide 16 a includes a base section 160, and a first wall section 161 and a second wall section 162 extending from the base section 160 in the sheet stacking direction. In order to enable the first side guide 16 a and the second side guide 16 b to slide in linkage with each other, a coupling rail 163 couples both to each other. The coupling rail 163 fixes the base section 160.

The first wall section 161 includes the guide surface 161 a, a stackable position indicator 161 b and a protrusion 161 c.

As stated above, the guide surface 161 a positions the edge of the sheet in the Y-axis direction.

The stackable position indicator 161 b indicates, by the position (height) of the sheets in the stacking direction, the maximum stacking amount of sheets capable of being stacked on the sheet tray 14. The stackable position indicator 161 b is indicated on the guide surface 161 a.

The protrusion 161 c pushes up the edge of the sheet falling in the opening 14 b of the sheet tray 14 to the same position as the sheet stacking surface of the sheet tray 14 and supports it. Since the stackable position indicator 161 b indicates the maximum stacking position with reference to the stacking surface of the sheets on the sheet tray 14, when the protrusion 161 c pushes up the edge of the sheet at the guide surface 161 a side and supports it, the stacking amount of sheets relative to the stackable position indicator 161 b can be accurately grasped.

The after-mentioned sheet edge guide 20 is positioned at the first wall section 161 side of the base section 160 and between the protrusion 161 c in the X-axis direction and the sheet tray 14.

Next, the end guide 18 slides in the X-axis direction, and positions one edge of the sheet in the X-axis direction. The position of the stacked sheets in the X-axis direction is determined by the end guide 18 and the side wall section 12 c of the cassette case 12. For example, in the state where the sheet is placed next to the side wall section 12 c, the end guide 18 is slid until it strikes against the edge of the sheet, and the movement in the X-axis direction is regulated to perform positioning. Alternatively, the end guide 18 is previously slid in accordance with the width of the sheet to be stacked, and the sheet is placed at the position defined by the end guide 18 and the side wall section 12 c, so that the sheet can be stacked at the position corresponding to the size of the sheet.

Next, a structure of the sheet edge guide 20 of the embodiment will be described in detail with reference to FIG. 5 to FIG. 7. FIG. 5 is a sectional view of the sheet cassette 10 at an arrow C-C position in FIG. 3, FIG. 6 is a sectional view of the sheet cassette 10 at an arrow D-D position in FIG. 3, and FIG. 7 is a perspective view of the sheet cassette 10 seen from the side wall section 12 c side (a downstream side in a sheet supply direction). Incidentally, in FIG. 5 to FIG. 7, for facilitating understanding, the stacked sheet S is illustrated. Besides, in FIG. 7, a portion of the sheet cassette 10 at the sheet supply direction downstream side of the edge of the first wall section 161 at the side wall section 12 c side is omitted.

As stated above, the sheet edge guide 20 of the embodiment is located at the position of the base section 160 along the guide surface 161 a of the first wall section 161 and at the sheet supply direction downstream side of the opening area of the opening 14 b of the sheet tray 14. When the sheet S is slid on the sheet tray 14 and is positioned to the stacking position defined by the first side guide 16 a, the end guide 18 and the like, the sheet edge guide 20 pushes up the corner of the sheet and prevents the corner of the sheet from being caught by or entering a step or a gap of the sheet tray 14 or the cassette case 12 adjacent to the sheet edge guide 20.

Specifically, as stated above, the sheet tray 14 includes the opening 14 b in the area where the first side guide 16 a slides and moves. The position of the upper surface of the base section 160 in the opening area of the opening 14 b is located at the position lower than the sheet stacking surface by approximately the thickness of the sheet tray 14 in the state where the sheet stacking surface of the sheet tray 14 is in the horizontal state, and the bottom 12 e of the cassette case 12 is located at the position further lower than the base section 160. For example, in the state where the side of the sheet is made coincident with the guide surface 161 a of the first side guide 16 a, in order to adjust the position of the sheet in the X-axis direction, when the sheet S is slid by the end guide 18 (or the sheet S is directly slid by the user's hand) and is moved to the side wall section 12 c side, the edge of the sheet, especially the corner Sc of the sheet strikes against the side (step) of the opening 14 b of the sheet tray 14, or enters between the sheet tray 14 and the bottom 12 e, and is caught. When the corner Sc of the sheet S is caught by the step or the like, there is a fear that the corner Sc is bent or torn and is damaged.

Further, as shown in FIG. 4, the sheet tray of the embodiment includes the cushion member 14 e on the bottom surface at the rotation shaft 14 a side in order to prevent a collision sound from being generated by dropping of the sheet tray 14. However, when the number of sheets stacked on the sheet tray 14 is small and the stacking weight is light, the elastic deformation of the cushion member provided on the sheet tray 14 becomes small. As compared with the case where a large number of sheets are stacked and the elastic deformation occurs, there occurs a state in which the sheet tray 14 at the other edge side opposite to the rotation shaft 14 a side rises. When the sheet tray 14 at the other edge side rises, for example, the step formed by the opening 14 b of the sheet tray 14 or the gap in the opening 14 b between the sheet tray 14 and the cassette case 12 becomes large, and the corner Sc of the sheet is liable to be caught by the step or the like.

As shown in FIG. 5, a guide surface 20 a as an inclined surface receives and pushes up the corner Sc of the sheet placed next to the sheet stacking position, and the sheet edge guide 20 guides the sheet so that the corner Sc of the sheet climbs over the step between the base section 160 and the sheet tray 14.

The sheet edge guide 20 of the embodiment is an elastically deformable sheet-like member having a triangular shape. One side of the triangle of the sheet edge guide 20 contacts the base section 160 below the sheet stacking surface of the sheet tray 14 and is fixed. In a rectangular sheet stacking area defined by the first side guide 16 a, the second side guide 16 b, the end guide 18, the side wall 12 c and the like in the cassette case 12, the guide surface 20 a of the sheet edge guide 20 is an inclined surface which is inclined with respect to any of the sheet stacking direction (Z-axis direction), the sheet supply direction (X-axis direction), and the direction (Y-axis direction) perpendicular to the stacking direction and the sheet supply direction, and becomes higher from the position of the upper surface of the base section 160 as the guide surface approaches the corner side of the sheet stacking area formed at the position where the extended line of the guide surface 161 a crosses the side wall section 12 c.

In other words, the guide surface 20 a is the inclined surface facing the three directions of the stacking direction (Z-axis direction) of the sheet S, the reverse direction to the supply direction (X-axis direction) of the sheet S (in other words, the direction from the side wall section 12 c side to the side wall section 12 d side), and the direction to the center side in the width direction of the sheet S. By this guide surface 20 a, the lower surface of the sheet S can be scooped without fail. Incidentally, the direction to the center side in the width direction of the sheet S is the direction from the side wall section 12 b to the side wall section 12 a when the sheet edge guide 20 is attached to the first wall section 161 of the first side guide 16 a, and is the direction from the side wall section 12 a to the side wall section 12 b when the sheet edge guide is attached to the side of the second side guide.

Incidentally, it is desirable that the direction of the guide surface 20 a of the sheet edge guide 20 is set so that the angle with respect to the guide surface 161 a is about 45 degrees on the horizontal surface (X-Y plane). When the angle is set to about 45 degrees, in both a case where the sheet S is shifted to the side wall section 12 c side from the side wall section 12 d side (arrow E direction of FIG. 7) and a case where the sheet is shifted to the side wall section 12 b side from the side wall section 12 a side (arrow F direction of FIG. 7), the sheet edge guide 20 receives and pushes up the corner Sc of the sheet, and prevents the corner Sc from contacting the step or the like.

Besides, it is desirable that the height of the sheet edge guide 20 in the sheet stacking direction is higher than at least the sheet stacking surface of the sheet tray 14 in the horizontal state. This is because, when the upper edge of the sheet edge guide 20 is higher than the position of the sheet stacking surface of the sheet tray 14, the corner Sc of the sheet can climb on the sheet stacking surface of the sheet tray 14 without fail.

The sheet edge guide 20 is fixed to, for example, a support member 20 s (see FIG. 6 and FIG. 7) arranged at the back side of the guide surface 20 a and is supported. As shown in FIG. 7, the support member 20 s is a stand-like member having an inclined surface for inclining and fixing the sheet edge guide 20. Incidentally, the support member 20 s has only to be able to support the sheet edge guide 20, and may be, for example, a plate-like member having an inclined surface formed by bending a plate.

Incidentally, when the sheet S is stacked at the position defined by the first side guide 16 a, the second side guide 16 b, the end guide 18 and the side wall section 12 c, the sheet edge guide 20 is elastically deformed by the weight of the sheet. It is desirable. that when at least sheets the amount of which is the maximum stacking amount of the sheet cassette 10 in a state where the sheet edge guide 20 is not provided are stacked on the sheet tray 14, the position of the upper edge of the sheet edge guide 20 in the sheet stacking direction is not higher than the height of the sheet stacking surface of the sheet tray 14. This is because when the upper edge position of the sheet edge guide 20 is higher than the sheet stacking surface of the sheet tray 14 even in the state where the original maximum stacking amount of sheets are stacked, a portion of the sheet S on the sheet edge guide 20 rises, and there occurs the same state as the state where the amount of stacked sheets exceeds the maximum stacking amount of the sheet cassette 10. Exceeding the maximum stacking position cause a paper jam or the like.

In the sheet edge guide 20 of the embodiment, since the sheet edge guide 20 is elastically deformed, the position of the upper edge of the sheet edge guide 20 in the state of covering the support member 20 s becomes almost equal to the position of the sheet stacking surface. Even if the sheet S is placed on the sheet edge guide 20, the surface (upper surface) of the sheet S is flat.

Besides, in the same reason, it is desirable that the sheet edge guide 20 of the embodiment is made of a material having such elasticity that when a maximum stacking amount of sheets are stacked, the sheet edge guide is deformed to a position lower than the sheet stacking surface of the sheet tray 14. As the material of the sheet edge guide 20, for example, a polyethylene terephthalate film, a film coated with Teflon, a polyester film or the like can be used.

Besides, it is preferable that the shape of the sheet edge guide 20 is a triangular shape. This is because when the sheet edge guide 20 falls to the support member 20 s side (bottom 12 e side of the cassette case 12) by the weight of the sheet and is elastically deformed, it is prevented that the deformed and falling portion of the sheet edge guide 20 contacts the guide surface 161 a of the first wall section 161 or the adjacent sheet tray 14. Incidentally, the triangular shape may be a shape having a round tip, or a trapezoidal shape or a fan-like shape may be adopted as a shape close to the triangular shape.

The above is the structure of the MFP 1 of the embodiment and the sheet cassette 10 of the MFP 1.

According to the sheet cassette 10 including the sheet edge guide 20 of the embodiment as described above, when the sheet contained in the sheet cassette 10 is slid on the sheet tray 14 and is positioned at the proper stacking position, the corner of the sheet does not strike against the step such as the side surface of the opening 14 b of the sheet tray 14, and the sheet can be moved. Accordingly, the edge of the sheet, especially the corner of the sheet is not bent or torn.

Besides, in the rectangular sheet stacking area defined by the first side guide 16 a, the second side guide 16 b, the end guide 18, the side wall 12 c and the like in the cassette case 12, the guide surface 20 a of the sheet edge guide 20 is the inclined surface which is inclined with respect to any of the sheet stacking direction, the sheet supply direction, and the direction perpendicular to the stacking direction and the sheet supply direction, and becomes higher from the position of the upper surface of the base section 160 as the guide surface approaches the corner side of the sheet stacking area formed at the position where the extended line of the guide surface 161 a crosses the side wall section 12 c. Thus, the sheet edge guide 20 receives and pushes up the edge of the sheet even when the sheet moves in either of the sheet supply direction and the direction from the side wall section 12 a side to the side wall section 12 b side, and can prevent the edge of the sheet from striking against the step or the like.

Besides, since the sheet edge guide 20 is an elastically deformable sheet-like member, when at least the maximum stacking amount of sheets are stacked, the sheet edge guide 20 is elastically deformed and falls. Thus, the sheet edge guide 20 does not push up the sheet to a position above the position of the sheet stacking surface of the sheet tray 14. Accordingly, the same amount of sheets as the maximum stacking amount of sheets in the case where the sheet edge guide 20 does not exist can be stacked.

Besides, since the sheet edge guide 20 is disposed on the base section 160 of the first side guide 16 a, even if the first side guide 16 a moves, the sheet edge guide 20 can keep the specific positional relation to the guide surface 161 a of the first side guide 16 a. When the sheet is shifted in the sheet supply direction by sliding of the end guide 18 or the like in the state where one edge of the sheet in the Y-axis direction contacts the guide surface 161 a of the first side guide 16 a, the sheet edge guide 20 can always push up the corner of the sheet, and can prevent the sheet from striking against the step or the like without fail.

Besides, when the shape of the sheet edge guide 20 is made triangular, even when the sheet is stacked on the sheet edge guide 20 and the sheet edge guide 20 is elastically deformed and falls, the deformed and falling portion does not contact the guide surface 161 a or the sheet tray 14.

Next, a sheet stacking method by the sheet cassette 10 of the embodiment will be described.

First, a sheet is placed on the sheet tray 14 in a state where the interval between the first side guide 16 a and the second side guide 16 b and the interval between the end guide 18 and the side wall section 12 c are made wider than the width of the sheet to be stacked.

Next, the first side guide 16 a and the second side guide 16 b are moved to perform positioning of the sheet in the Y-axis direction, the end guide 18 is moved to perform positioning in the X-axis direction, or positionings in the Y-axis direction and the X-axis direction are simultaneously performed.

When the positioning in the Y-axis direction is performed, the first side guide 16 a and the second side guide 16 b are slid until the interval between the first side guide 16 a and the second side guide 16 b coincides with the width of the stacked sheet in the Y-axis direction. The sheet is shifted to a proper stacking position in the Y-axis direction corresponding to the size of the sheet.

When the positioning in the X-axis direction is performed, the end guide 18 is slid until the interval between the end guide 18 and the side wall section 12 c coincides with the width of the sheet in the X-axis direction. The sheet is placed next to the side wall section 12 c as the reference position of one edge of the sheet in the X-axis direction.

When the positionings in the Y-axis direction and the X-axis direction are simultaneously performed, the first side guide 16 a, the second side guide 16 b and the end guide 18 are moved at the same timing.

When the first side guide 16 a and the second side guide 16 b are slid to perform the positioning of the sheet in the Y-axis direction, or when the end guide 18 is slid to perform the positioning of the sheet in the X-axis direction, or when the positionings in both the X-axis direction and the Y-Axis direction are performed at the same timing, while the corner of the sheet is pushed up by the sheet edge guide 20, the position of the sheet is made coincident with the stacking position corresponding to the size of the sheet.

For example, in the state where the positions of the first side guide 16 a and the second side guide 16 b are coincident with the positions of both ends of the sheet in the Y-axis direction and the positioning of the sheet in the Y-axis direction is performed, when the end guide 18 is slid and the sheet is shifted to the position of the side wall section 12 c as the reference position in the X-axis direction, the sheet is pushed by the end guide 18 and is moved in the sheet supply direction (direction from the side wall section 12 d side to the side wall section 12 c side). The corner of the sheet is pushed up by the sheet edge guide 20, and the sheet is moved without being caught by the step caused by the opening 14 b of the sheet tray 14 or the like.

Besides, in the state where the positions of the end guide 18 and the side wall section 12 c are coincident with the positions of both ends of the sheet in the X-axis direction, and the positioning of the sheet in the X-axis direction is performed, when the first side guide 16 a and the second side guide 16 b are slid, and the sheet is shifted to the proper stacking position in the Y-axis direction, the sheet edge guide 20 of the first side guide 16 a enters the lower side of the sheet and pushes up the corner of the sheet. Since the edge of the sheet is located at a position where the edge already passes the step caused by the opening 14 b of the sheet tray 14, the sheet edge guide 20 does not push up the sheet to cause the edge of the sheet to climb over the step. However, since the guide surface 20 a of the sheet edge guide 20 is directed also to the direction of the shifted sheet, the sheet is not caught by the side surface of the sheet edge guide 20. Even if the positioning in the Y-axis direction is performed after the positioning in the X-direction, the sheet edge guide 20 can receive the edge of the sheet while being elastically deformed.

When the first side guide 16 a, the second side guide 16 b and the end guide 18 slide at the same timing and perform the positioning of the sheet, similarly to the case where the sheet is moved in the sheet supply direction, the corner of the sheet is pushed up by the sheet edge guide 20. Accordingly, the sheet is not caught by the step caused by the opening 14 b of the sheet tray 14 or the like, and is moved to the stacking position corresponding to the size of the sheet.

As described above, according to the sheet stacking method of the embodiment, when the sheet is moved to the stacking position corresponding to the size of the sheet by the side guide or the end guide, since the sheet edge guide 20 pushes up the corner of the sheet, the corner of the sheet is not caught by the step caused by the opening 14 b of the sheet tray 14 or the like.

Incidentally, in the embodiment, the description is made on the assumption that the sheet edge guide 20 is located at the position along the guide surface 161 a on the base section 160 of the first side guide 16 a and at the sheet supply direction downstream side in the opening area of the opening 14 b of the sheet tray 14. The position of the sheet edge guide 20 can be set within a range where the corner of the sheet pushed up by the sheet edge guide 20 can climb over the step of the sheet tray 14 according to the conditions such as the height of the sheet edge guide 20 in the sheet stacking direction, the inclined angle and direction of the guide surface 20 a, the degree of elasticity of the sheet edge guide 20, and the thickness and hardness of the sheet to be stacked.

Besides, in this embodiment, the description is made on the assumption that the sheet edge guide 20 is fixed to the base section 160 of the first side guide 16 a. The sheet edge guide 20 may be similarly provided at the corresponding position of the base section of the second side guide 16 b opposite to the first side guide 16 a.

Besides, in this embodiment, the description is made on the assumption that the sheet edge guide 20 is fixed to the base section 160 of the slide-type side guide. When the side guide to which the sheet edge guide 20 is disposed is not of the slide type but of a fixed type, the sheet edge guide 20 may be directly fixed to the bottom 12 e of the cassette case 12.

Besides, in this embodiment, the description is made on the assumption that the sheet cassette 10 includes the first side guide 16 a and the second side guide 16 b sliding in linkage with each other in order to position the sheet at the center position of the sheet cassette 10. For example, one of the side guides (for example, the second side guide 16 b) is fixed to the cassette case 12, and only the other side guide (the first side guide 16 a) may slide. Alternatively, the side wall section 12 a (or the side wall section 12 b) is made the reference position in the Y-axis direction and positioning may be performed. Since the sliding side guide (the first side guide 16 a or the second side guide 16 b) has the sheet edge guide 20, when the side guide or the end guide slides and the sheet moves, since the sheet edge guide 20 pushes up the sheet, the sheet does not strike against the step of the sheet tray 14 or the like and the sheet is not damaged.

Besides, in this embodiment, the description is made on the assumption that the sheet edge guide 20 is the elastically deformable sheet-like member. However, any member may be used as long as the member is elastically deformed while pushing up the sheet. For example, a block-like rubber having the guide surface 20 a or a sponge may be used as the sheet edge guide 20.

As described above in detail, according to the technique disclosed in this specification, the sheet supply device can be provided in which sheet positioning can be performed without damaging the sheet.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of invention. Indeed, the novel apparatus and methods described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the apparatus and methods described herein may be made without departing from the sprit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 

1. A sheet container comprising: a case configured to contain a plurality of sheets stacked in a stacking direction; a first regulating member configured to regulate a first side of the sheets along a first direction perpendicular to the stacking direction; a second regulating member configured to regulate a second side perpendicular to the first side along a second direction perpendicular to the stacking direction and the first direction, the second regulating member to form a rectangular area with the first regulating member under the sheets; a tray configured to support a lower surface of a lowermost sheet of the sheets; and a guide member inclined with respect to the stacking direction, the first direction and the second direction on the rectangular area, and formed higher from a position lower than the lower surface of the lowermost sheet as approaching a closest corner in the rectangular area.
 2. The container of claim 1, wherein the first regulating member moves in the second direction.
 3. The container of claim 2, wherein the guide member moves together with the first regulating member.
 4. The container of claim 3, wherein the guide member moves from an outside position of the first side of a sheet having a maximum width in the second direction among the stacked sheets to an inside.
 5. The container of claim 3, wherein the tray comprises a stacking surface to support the lower surface of the stacked sheet in an area except an area where the first regulating member moves.
 6. The container of claim 1, wherein the guide member comprises a triangular shape.
 7. The container of claim 6, wherein one side of the guide member is along a bottom of the case.
 8. The container of claim 1, wherein the guide member is elastically deformed by weight of the stacked sheets, and is displaced in a direction of approaching a bottom of the case.
 9. The container of claim 8, wherein the guide member is elastically deformed in a space where the guide member does not contact the first regulating member.
 10. The container of claim 1, wherein the guide member is a sheet-like member.
 11. The container of claim 10, further comprising a support member to support a posture of the guide member.
 12. The container of claim 1, further comprising a cushion member which is positioned between the tray and a bottom of the case and is elastically deformed by receiving weight of the tray.
 13. The container of claim 1, wherein an edge of the guide member is positioned above a stacking surface of the tray to support the lower surface of the stacked sheet.
 14. The container of claim 13, wherein when a maximum stacking amount of sheets is placed on the tray, the guide member receives weight of the stacked sheets and is elastically deformed, and the edge is displaced to a position lower than the stacking surface.
 15. The container of claim 1, wherein the first regulating member includes a wall to regulate the first side of the sheets and a base section to support the wall, and the guide member is positioned on the base section.
 16. An image forming apparatus comprising: a sheet container including a case configured to contain a plurality of sheets stacked in a stacking direction, a first regulating member configured to regulate a first side of the sheets along a first direction perpendicular to the stacking direction, a second regulating member configured to regulate a second side perpendicular to the first side along a second direction perpendicular to the stacking direction and the first direction, the second regulating member to form a rectangular area with the first regulating member under the sheets, a tray configured to support a lower surface of a lowermost sheet of the sheets, and a guide member inclined with respect to the stacking direction, the first direction and the second direction on the rectangular area, and formed higher from a position lower than the lower surface of the lowermost sheet as approaching a closest corner in the rectangular area; an image forming section to form an image on the sheets; and a conveying section to convey the sheets stacked on the case to the image forming section.
 17. The apparatus of claim 16, wherein the first regulating member moves in the second direction.
 18. The apparatus of claim 17, wherein the guide member moves together with the first regulating member.
 19. The apparatus of claim 16, wherein the guide member comprises a triangular shape.
 20. A sheet stacking method for a sheet container including a case configured to contain a plurality of sheets stacked in a stacking direction, a first regulating member configured to regulate a first side of the sheets along a first direction perpendicular to the stacking direction, a second regulating member configured to regulate a second side perpendicular to the first side along a second direction perpendicular to the stacking direction and the first direction, the second regulating member to form a rectangular area with the first regulating member under the sheets, a tray configured to support a lower surface of a lowermost sheet of the sheets, and a guide member inclined with respect to the stacking direction, the first direction and the second direction on the rectangular area, and formed higher from a position lower than the lower surface of the lowermost sheet as approaching a closest corner in the rectangular area, the stacking method comprising: stacking a plurality of sheets on the tray; and moving the stacked sheets in the first direction while a corner of the sheets is placed on the guide member. 